Automatic stoker



April 3, 1928. 6,903

J. S. SKELLY AUTOMATIC STOKER Filed Au 24. 1923 s Sheerls-Sheet 2 FIG. 3.

INVENTOR April 3, 1928.

J. s. SKELLY AUTOMATIC STOKER Fi] .ed 24, 1923 s Sheets-Shet I 5 FIE-3- IN E N TOR Patented Apr. 3, i928.

COMBUSTION ENGINEERING CORPORATION, A

CORPORATION OF DELAWARE.

AUTOMATIC STOKER.

Application filed August at, 1923. Serial No. 6591130.

This invention relates to automatic stokers and particularly to underfecd stokers.

An object of the invention is to produce a Stoker of the type specified in which improved means are employed for delivering fuel tothe stoker, for supporting and propelling the fuel through the combustion chamber of the stoker, and for discharging the ash or refuse material from the combustion chamber.

In underfeed furnaces, the fuel is delivered to the furnace or to the combustion chamber of the furnace, in such a way that it is subjected to the sensible heat of combustion within the furnace-before it is supplied with suiiicient air to promote combustion. Under such conditions, the fresh or green fuel on being introduced into the furnace is subjected to a coking operation during which the volatile hydrocarbon gases are distilled off and pass through previously delivered fuel and a portion of the burning fuel bed in its travel toward the stack or the combustion space within the furnace above the fuel bed.

Under such conditions, it is desirable to break up the coked mass resulting from the coking o1 eration, as it moves upwardly into the air delivery zone. I have found that it is desirable to control this breaking up process to a greater extent than in existing stol-iers. I accomplish this in the stoker illustrated by employing a special form of fuel supporting elements so located and arranged with relation to the retort that effectivc breaking up of the coked mass issuing from the retort is somewhat delayed as the fuel progresses toward the rear, or refuse delivery end of the stoker. With such apparatus it is possible to materially increase the fuel burning capacity of the furnace, per square foot of grate surface, and to obtain substantially complete combustion of the fuel without producing smoke.

'i further object of the invention is, therefore to produce a furnace equipped with an automatic stoker in which means are cmploycd' for improving the fuel-burning conditions by controlling the breaking-up of the coked mass issuing from the retort in such a way that a complete breaking up f the mass is deferred for an appreciahlc pn'iod as the cokcd mass progresses toward or the ash discharge mechanism.

Other objects not specifically specified will be made more apparent throughout the further description of the invention.

in the drawings accompanying and form iug a part hereof, Figure 1 is a longitudinal sectional elevation of a Stoker embodying my invention. Fig. 2 is a fragmental sectional elevation of a modified form of grate bar forming a detail of the present invention. Figure 3 is a side elevation of the stol er illustrated in Fig. 1, and illustrates the particular form of operating mechanism employed; Fig. 4 is a fragmental perspective view of the apparatus illustrated in Fig. 1.

The stoker illustrated as an embodiment of my invention includes a grate made up of two series 5 and 6-of rearwardly extending grate bars located in parallel relation. A transversely extending retort 7 is located at the front of the stoker and extends substantially the entire width of the grate. Fuel is delivered to the retort on the side'remote from the grate through a fuelreceiving opening which extends substantially the entire width of the grate. A fuel hopper 9 is located at the front of the furnace and extends across the furnace substantially the entire width of the fuel-removed back and forth across the mouth of the hopper 9' by a continuously operating machanism hereinafter more fully described.

As shown in the drawings, the retort 7 is provided with a horizontal floor 11, ex tending the entire length of the retort and of such width that itprojects through the fuel receiving opening formed in the front wall 13 of the stoker and forms the bottom of a passage 12 into which fuel from the hopper is delivered and through which fuel is propelled into theretort by the action of the plungers 10. The passage 12 is commensurate in width with the length of the retort 7 and is so located and arranged that there is no clear line of demarcation between it and the retort. As shown the passage is located between the floor 11 and atop plate 141- which is inclined upwardly in the direction of the fuel feed, thereby providing a passage with gradually diverging walls which increases in depth from the fuel admission end toward the retort and is deeper at the retort end than the retort.

The rear of the retort is defined by the forward ends of the grate bars con'iprising the series 5. The height of those grate bars above the floor 11, therefore, defines the depth of the retort. As shown, the series 5 is made up of alternately arranged moving and stationary bars 15 and'16, which extend from the retort 7 toward the rear of the stoker and are so constructed and arranged that their rear portions are inclined downwardly, in the direction. of fuel travel, and deliver fuel onto the second series 6.

As shown the grate bars 15 and 16 are supported'attheir forward ends on the upper edge of the floor 11 and at their rear ends on a transverselyextending member 17, forming a part of the supporting structure of the Stoker. These grate bars are hollow, each being providedthroughout their length with an air delivery passage 18 having an inletport at the lower side near the forward end of the bar, and an outlet at the lower side near the rear end of the bar. The forward end of each bar is substantially wedge shaped and so formed that it presents an upwardly-inclined surface 00 to the fuel issuing from the retort 7. This surface terminates in a substantially horizontal fuel supporting surface 7 which extends toward the rear of the stoker. The horizontal surface of each bar is followed by a downwardly-inclined surface .2 which is continuous witlr the horizontal fuel supporting surfacebut which abruptly falls away from the surface 1 as to provide a well deiined angle or shoulder over which the fuel is propelled as it leaves the horizontal surface of the bar. The lowereuds'of the bars of the series 5-are sul'istantially wedge shaped but are rounded off so as reform a more or less abrupt too 19 which engages the top surface of theone of the bars of the-,series Gand has the effect of a pi'isher for aiding the rear ward propulsion of fuel over these bars.

From the foregoing it will be apparent that each grate bar of the series 5, is provided with substantially wedge shaped ends and that the fuel supporting surface between the ends comprises in effect surfaces which extend at a moreor less abrupt angle to each other and thereby provide a well defined shoulder over which the fuel passes inmoving from: one part of the supporting surface to the other.

The series 6 includes alternately-arranged moving'andstationary grate bars 21 and 22 which extend in the direction of fuel travel and which are supported at their forward ends on the member 17 and at their rear ends on a partition wall 23. The wall 23 forms a part of the stokersupporting structure and also separates an ash-receiving receptacle 24 formed at the rear of the stoker from an air chamber 25 located below the bars 21 and 22 of the series 6.

Each of the grate bars 21 and 22 is hollow, being provided with an air passage 20 which extends substantially the length of the bar and provided at the forward end witlran air inlet port opening through the bottom of the bar and at the rear end with an air delivery port also opening. through the bottom of the bar. Each bar is also so constructed that its forward end provides a substantially horizontal fuel supporting surface which terminates in a downwardly-inclincd fuelsupportingsurface extending to the rear end of the grate bar. The inclination of the rear portion of each grate bar is, however, substantially less than. the inclination of the rear portion of each of the grate bars 1516.

The space below the grate bars-is divided into two air chambers 25 and 26. As has been stated, the chamber 25 is located below the bars of the series 6. The chamber 26 is located below the bars of. the series 5. Each of these air chambers receives air under pressure from a conduit or passage 27 but the air traverses the air passages of one of the series of grate bars before it enters either air chamber. As shown in Fig. 1, anupwardly extending branch passage 28 leads off from the conduit 27 and delivers air under pressure to the passages 18 of the grate bars 15 and 16. This passage 28 is bounded by transversely-extending partition plates 29 and 30. The upper end of the. passage 28 terminates in a transversely extending port located between the rear edge of the floor 11 and a transversely-extending member 31 which forms a part of the sup-- porting. structure of the stoker. The port registers with the inlet ports of the passages 18 of the grate bars 15 and 16 and consequently the chamber 26 receives air from the passage 28 after it has traversed the hollow grate bars 15 and 16. ith this arrangement, the grate bars are cooled by the incoming air and the major portion of the air delivered to the fuel bed is therefore preheated.

The grate bars of the series 5 are spaced apart a sufficient distance to provide airdelivery spaces between them through which air delivered to the chamber 26 passes upwardly into the fuel bed.

Air is delivered to the chamber 25 througl'i a branch passage 32 and the air passages 20 of the bars 21 and 22. The branch passage is located between iartition plates 33 and 23-51 which respectively separate the passage lit} lit;

Ill)

each of the grate bars.

from the chambers 26 and 25. The upper endof this passage terminates in a transversely-extending port formed between a support member 35 of the stoker structure and the support member 17. The bars of the series 6 are also spaced so as to provide air passages between them through which preheated air from the chamber 25 is delivered to the portion of the fuel bed supported by the'bars.

Air is also delivered directly to the fuel bed from the passage 32 through the spaces between the grate bars. In addition to this, air delivered directly from the passages 20 of each grate bar 21 and 22 to the fuel bed. This is accomplished by providing air ports 36 in the fuel-supporting surface of As shown, the air ports are preferably so arranged that air is delivered at the forward ends only of these bars and, in addition, the ports are so spaced that the greater portion of the air from the-passage 20 is admitted at a point immediately adjacent to'the lower ends of the bars 15 and 16.

One of the features of the present invention is the arrangement of the air ports in the fuel-supporting surfaces of the bars 15 and 16. As shown in Fi 1, each of these bars is provided with air ports 37, adapted to deliver air from the. passages 18 to the fuel bed. The ports are arranged in the forward portion of the bars only and are preferably so spaced that the quantity of air delivered through these to the fuel bed increases as the fuel progresses toward the rear of the stoker. It will also be apparent that some air is delivered to the fuel bed directly from the passage 28 through the spaces between the grate bars.

The passages 28 and 32 are respectively provided with dampers 38 and 39 which may be independently controlled.

It will thus be apparent that the delivery of air to the front and rear portions of the stoker may be independently controlled and that, in addition to this, the air is so delivered to the fuel bed that two distinct zones of increased air supply are provided. Each of these zones is located near the forward end of one of the two series of grate bars and the delivery of air to each is controllable independently of the other.

In Fig. 2, I have shown a modified form of grate bar which may be employed in place of the bars 15 and 16. As illustrated, this bar is provided with a wedge shaped forward end which presents a steep and somewhat elongated inclined surface a to the fuel issuing from the retort. This surface terminates in a relatively short substantially horizontal fuel-supporting surface g which terminates in a downwardly inclined surface- 2 of such abruptinclination as to present a well-defined shoulder over which the fuel passes in moving onto the rear portion of the grate bar. The rear portion of the grate bar is inclined downwardly toward the rear so as to provide a downwardly-inclined fuel-supporting surface 2. The angle of this surface is, however, materially less than that of the surface .2. As shown, the surfaces zv' and y are provided with air ports 37, through which air is delivered from the passage 18 into the fuel bed.

Another feature of my invention is the fuel-disposal mechanism located at the rear end of the stoker and employed in connection with the receptacle 2 1. As shown, a pivotally mounted ash-regulating gate 41 is provided immediately below the rear ends of the bars 21 and 22. This gate is capable of being tilted to different angular positions for the purpose of varying the angle of delivery to a rotating grinder 43, which rotates in the direction indicated by the arrow. The principal function of this tilting gate is to deliver refuse material discharged from the grate bars 21 and to the grinding roll or to by-pass the grinding roll so such material is dropped from the bars 21 and 22 into the. bottom of the receptacle 24. To this extent the gate functions as a dump grate, since it may either be elevated to the position shown in full lines in Figure 1, where it acts as a fuel-bed support member, or it may be tilted to the dotted-line position for the purpose of dumping the accumulation of ash and clinker into the bot-tom of the receptacle. In order that I may employ the gate 11 in this way and also adjust it to different angular positions, I preferably operate it by means of a worm H and worm wheel segment 45, shown in Fig. The se ment 15 is mounted on the shaft of the gate and is located outside but adjacent to one side wall of the stoker. The worm 41 is preferably operated by hand by means of a ratchet-and-pawl m chanism, not shown.

The grinder is of the usual construction and, as illustrated, consists of toothed discs mounted on asquare shaft. 1t preferably rotates at the top toward the bridge all 15 so that the clinker breaking effect. is accomplished between it and the bridge wall. For the purpose of rendering the grinder more efficient in operation, I employ what may be termed a. grinder back 46, which is located immediately above the grinder so that refuse material passing over the grinder must pass between it and the back. As shown, the back 46 is hollow and is preferably water-cooled. This arrangement has two advantageous features. It prevents the sticking of clinker to the rear wall of the stoker above the grinder and it also has some cooling effect on the clinker and ash passing to the grinder andinto the bottom of the receptacle. The receptacle is iu'ovided with a spiral conveyorAF which is preferably operated bythe operating mechanism of the stoker so as to remove the refuse material delivered to the receptacle at about: the rate of its delivery to the receptacle.

Another feature of my invention is that the front plate 14-, forming the top of the fuehdelivery passage l2, is air-cooled.

This is iu'complished by making the. plate a part of an oblong enclosure 48 to which airdelivered and from which air is discharged into the combustion chamber of the furnace through conduits or passages it). As shown, the passages 4-9 extend through the front wall 13 of the furnace some distance above the fucl-suppm'ting grate.

The fuei-delivery means 10 preferably consists of a number of plungers located adjacentto each other and so arranged that the passage 12 throughout its entire length is a fuel-deliverii'ig passage. lVhile single plunger of the length of the p ssagie could be employed, for convenience of manufacturing and also for convenience of operation, Ipreferably employ sectional plunger-s and an. o )erating mechanism so arranged that some of the plungers are moving through the fuel feeding stroke toward the retort while others are being withdrawn from the retort.

As illustrated, each plunger or plunger section is operated by means of a reciprocating carriage 51 which is mounted on a suitable frame at the front of the stoker and is operatively connected to the plunger bymeans of a-detachable link As shown, the link is pivotally secured to the carriage and is provided near its free end with a slot which is adapted to engage a pin 53 carried by the plunger 10, and which permitsthe link to be detached from the plunger.

Each carriage is actuated by means of a crank 54 carried by a crank shaft 55. The crank is located within the carriage and the walls of the carriage are so constructed that they are first engaged at one side by the crank for the purpose of moving the carriage through. a fuel-feeding! stroke, and then at the other side for the purpose of retracting the carriage. Any suitable means may be employed for driving the shaft 55 but, as illustrated, itis oriven from a drive shaft 56 through the agency of intcrmeshinggears 57 and 57.

A feature of my invention is that the moving bars 15 of the upper series of bars are aligned with and cooperate with the stationary bars 22 of the lower series, whereas the moving bars 21 of the lo series are aligned with and cooperate with stationary bars 16 of the upper series. The operating mechanism of the moving bars of each series is preferably driven from the shaft As shown inthe drawings, the moving bars of the series 5 are actuated by means of a rocking arm 58 which extends transversely of the bars and is operatively coupled thereto by means of lugs 59 formed integrally with the bars. A similar arrangement of apparat'us is employed in connection with the moving bars of the. series ti and, as illustrated, these bars are actuated by means of a rocker arm 60 and lugs (it associated with the moving bars. As shown in Fig 3, the operating shafts as; of both the arms 5b and (50 project through a side waltof the furnace andeach is provided with an operating lever 63. These lovers are actuated through intcrconnectingr links (i i and as by means of a lever 66. The lever as is pivoted at a point intermediate its ends and is oscillated by a crank 67 mounted on the shaft and connecting rod (38. The lower end of the lever slotted to receive a pin (it) carried'by the link 65 anclis provided with ratchets 70 adapted to be engaged by a pawl, not shown, for the purpose of locking; the link in different positions along the lever and thereby varying the throw of the rocker bars 58 and 60. As shown in the drawings, the conveyor s7 is actuated by means of a sprocket-'71, chain. 72 and sprocl-zet T2}. The sprocket 71 is mounted on. the conveyor shaft and the sprocket 73 mounted on the drive shaft 56. I

The operation of the stoker is as follows: The reciprocating plungers 10 force fuel, delivered from the hopper 9, forwardly into the passage 12 through the passage and into the retort. The crowding action of the fuel entering the retort completely fills the diverging portion of the passage, and at-the time the divergence of this passage prevents undue packing of the fuel to such an extent as to impede the delivery of fuel into the retort. The fuel so delivered by the plungers fills and piles up in the retort until the retort overflows onto the grate bars of the series 5. After the fuel is established on the. fuel-supporting grate, the fuel leaving the retort is crowded upwardly by oncoming fresh fuel so that the fuel bed is built up from below and to a considerable heightabove the retort and above the forward ends of the grate bars and 6. The rearward travel of the fuel issuing from the retort is maintained by the propelling action of the reciprocating or moving bars of each series.

The motion imparted to these bars is a horizontal reciprocation so that each moving bar first moves rearwardly beyond the fuelsupporting surfaces of the stationary bars. With the bars 1: and 16 cmritrneted as dis-- closed in Fig. 1 or in Fig. 2, the propelling action of the (ilowmvardly inclined rear porill) tions of the bars is quite marked. whereas the a horizontal fuel-supporting portions of the bars occasion little propelling effect and practically no breaking up of the fuel bed. As

.of the retort of the coked mass.

' the'fuel issues from the. retort, it is subjected to the breaking-up action of the moving bars 15 'as they move forwardly into the confines as defined by the forward ends of the stationary bars and rearwardly out'of the jretort' as so defined. This action is sufiicient to aid in the rearwardpropulsion, and upward lift of the fuel and to prevent jamming of the fuel in the retort. It also facilitates the delivery of air to the coked mass issuing from the retort but it does not occasion a complete or thorough breaking up The fuel located on the horizontalportion y of the-grate bars 15 and 16 is subjected to little or no propelling action and to no breaking up action consequently, the fuel bed builds up over the horizontal portions and its rearward progress is primarily occasioned by this building-up action. This produces a relatively deep fuel bed at the forward end of the stoker, which is desirable. It is, however, desirable to break up this fuel bed as the fuel starts to moye more rapidly across the grate so that it Wlll thin out toward the rear end of the stoker. This breaking-up action is effectively accomplished by employing bars so formed that the fuel leaving the horizontal portion passes over a well-defined shoulder and also moves down a relatively steep incline composed of alternately arranged stationary and moving bars.

The reciprocations of the moving bars, as well as gravity, acts to break up the fuel bed and to accelerate its rearward movement of the fuel toward the rear of the stoker. The grate bars comprising the series 6 to some extent check the rearward propulsion of the fuel due to the fact that the inclination is materially less than the inclination of the bars of the series 5. "Ihe moving bars of this series, however, occasion a uniform feed of fuel and prevent an undesirable thickening of the fuel bed. The entire arrangement of elements occasions an effective burning of fuel by maintaining a fuel bed of desired contour and by delivering excess air to certain portions of the fuel bed.

As has been described the ash and clinker are delivered to the clinker grinder roll 43 across the gate 41 and this gate may be dropped for the purpose of bypassing the grinder roll if desired.

While I have described, what I now consider to be the preferred embodiment of my invention it will be apparent to those skilled in the art that various additions, omissions, changes and modifications may be made in the apparatus illustrated without departing from the spirit and scope of my invention as set forth by the appended claims.

What I claim is:

1. In combination in a stoker, a retort extending substantially entirely across the frontof the stoker, a series of alternately arranged moving and stationary grate bars located in parallel relation and extending from said retort toward the rear of the stoker, each of said bars having a wedge shaped forward end provided with air delivery apertures in the fuel supporting surface thereof, a substantially horizontal fuel supporting surface located immediately adjacent to the wedge shaped end and having air delivery apertures formed therein and a downwardly inclined fuel supporting surface extending from'the horizontal surface toward the rear end of the stoker, and means for feeding fuel through said retort and on to the forward ends of said grate bars.

2. In combination in a stoker, a retort extending substantially entirely across the front of the stoker, a series of alternately arranged, moving and stationary gratebars, located in parallel relation and extending from said retort toward the rear of the stoker, each grate bar of said series having a Wedge shaped forward end provided with air delivery apertures in the fuel supporting surface thereof, a substantially fiat fuel supporting surface extending at an angle to the fuel supporting surface of the wedge shaped end and a fuel supporting surface extending downwardly at an abrupt angle from the last mentioned fuel supporting surface, means for propelling fuel transversely across said retort and on to the wedge shaped ends of the said bars and means for reciprocating the moving bars of the series.

3. In combination in a stoker a retort extending across the front of the stoker, a series of longitudinally arranged, moving and stationary grate bars, located in parallel relation and extending from said retort toward the rear of the stoker, each grate bar of the series having an upwardly inclined forward fuel supporting surface, a downwardly inclined rear fuel supporting surface and an intermediate substantially horizontal fuel supporting surface contiguous to both 'said first mentioned surfaces, a second series of alternately arranged moving and stationary grate bars moving in parallel relation and extending from the rear ends of the first series toward the rear of the stoker, the bars of the second series having fuel supporting surfaces extending at an angle to the rear supporting surfaces of the bars of the first series and being provided with air delivery apertures in the forward portions thereof.

4. In combination in a stoker, a retort extending across the front of the stoker, a series of alternately arranged moving and stationary grate bars located in parallel relation and extending from the retort toward the rear of the stoker, each of said grate bars having three substantially flat fuel supporting surfaces, located at an angle one to the other whereby the direction of the travel of the fuel varies as the fuel moves longitudinallyof said bars, means for delivering fuel transversely through said .retortvand on to said bars .anduneans for reciprocating the .m0vab1e bars of the series.

5. In combination in a stoker, a retort ex- .tendin across the front of the stoker. a series of grate bars extending in parallel relation from said retort toward therear of the Stoker, a reciprocating, means extending substantially entirely along the length of said retort for. delivering fuel thereto, each of the grate bars of said series having a Wedge shapedforward end, a substantially horizontal fuel supporting surface immediately adjacent said Wedge shaped end and MGM ,6. :In combinationin, a, stoker, a retort extendingaerossithe[front of the stokenfla series of grater bars located r in parallel-relation and extending from the, front toward the i'eaiuoftlie Stoker, eaclrgrateflbar of the seirieshavinga wedge shapedforward end provided witlrair delivery apertures,- aflo'wnwardly inclined rear {end and an extended substantially flat? intermediate fuel. support.

.ing suriaeev provided with air delivery, apertures and located atanaangle to the adjacent fuel supporting sn -laces ofsaidhar, whereby fuel itra versiingthe :bar ,is subjected to a breaking action in moving one fuel supporting. surface to. the other.

In testimony :Whereof, I have hereunto subseribml my name, this 7th day of August,

JOHN KE LY- 

